Technical Field
The present disclosure is related to a scheme adopting an unlicensed spectrum communication in a wireless communication system, and more particular to a communication method and device for an unlicensed spectrum based on Long Term Evolution (LTE).
Related Art
3rd Generation Partner Project (3GPP) defines a time division duplex (TDD) frame structure in a LTE system, as shown in Table 1, wherein D indicates a downlink sub frame, U indicates an uplink sub frame, and S is a special sub frame.
Table 1: TDD LTE Frame Structure.
Downlink-TDDuplinkframeswitchingSub frame index numberstructurepoint period0123456789#05 msDSUUUDSUUU#15 msDSUUDDSUUD#25 msDSUDDDSUDD#310 ms DSUUUDDDDD#410 ms DSUUDDDDDD#510 ms DSUDDDDDDD#65 msDSUUUDSUUD
R (Release) 12 of 3GPP introduces an enhanced interference management traffic adaptation (eIMTA) technique. That is for the TDD frame structure, it is capable of adjusting the TDD frame structure through a dynamic signaling. The possible TDD frame structure includes seven TDD frame structures #0-#6 defined by the LTE.
In a traditional 3GPP LTE system, data transmission may only occur on a licensed spectrum. However, with the sharp increase on the communication amount, especially in some urban areas, it may be difficult for the licensed spectrum to meet the requirement of the communication amount. 3GPP RAN (Radio Access Network) #62 meeting discussed a new research topic, i.e. a research of the unlicensed spectrum (RP-132085). The main purpose is to research the use of a non-standalone deployment of LTE on the licensed spectrum. The so-called non-standalone means that the communication on the unlicensed spectrum is associated with a serving cell on the licensed spectrum. An intuitive method is to reuse a concept of a carrier aggregation (CA) in the existing system as much as possible, i.e. a serving cell deployed on the licensed spectrum serves as PCC (Primary Component Carrier), and a serving cell deployed on the unlicensed spectrum serves as SCC (Secondary Component Carrier). The CA includes traditional TDD CA, FDD (Frequency Division Duplex) CA and FDD-TDD CA introduced by 3GPP R12. In RAN #64 meeting (seminar), the communication on the unlicensed spectrum is uniformly named as LAA (License Assisted Access).
For LAA, the mainstream of the application scenario is a small cell communication, i.e. the small cell supports the PCC deployed on the licensed spectrum and the SCC deployed on the unlicensed spectrum at the same time, and a macrocell supports the PCC deployed on the licensed spectrum. Compared to the licensed spectrum, it is more difficult to predict/control the interference on the unlicensed spectrum. Therefore, one viable method is that the control signaling is transmitted on the PCC and the data is transmitted on the SCC. However, the above method has the following problem.
For the small cell, the technique, such as eICIC (enhanced Inter Cell Interference Cancellation) or FeICIC (Further eICIC) and so on, makes the small cell only transmit PDCCH (Physical Downlink Control Channel) and PDSCH (Physical Downlink Control Channel) on the specific sub frame of the PCC, so as to avoid the interference with the macro cell. In the sub frame without transmitting the PDCCH, the small cell may not schedule the SCC.
If the PCC of the small cell adopts the traditional TDD or TDD eIMTA, the sub frame of the SCC corresponding to the uplink sub frame of the PCC may not be scheduled.
For the above problem, the present disclosure provides a communication method and device on an unlicensed spectrum in a UE and a base station.